JPH028395B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a track position correction device used in magnetic disk devices such as floppy disk devices, or optical disk devices that optically record and reproduce video and audio. be.

1. Structure of a conventional example and its problems FIG. 1 shows a conventional head positioning device for a magnetic disk device. In FIG. 1, 1 is a stepping motor, 2 is a capstan attached to the output shaft of the stepping motor 1, and 3 is an actuator arm whose one end is fixed to a shaft 4.
The other end of this actuator arm 3 is formed with a circular arc surface. The above actuator arm 3 and capstan 2 are connected to a steel belt (not shown).
are connected with. That is, the band-shaped steel belt is wound around the outer peripheral surface of the capster 2, and both ends are fixed to the ends of the arcuate surface of the actuator arm 3. A head arm 5 has one end fixed to the shaft 4. A head spring 6 is fixed to the other end of the head arm 5, and a head 7 is supported on the head spring 6.

In FIG. 1, when the stepping motor 1 operates, the capstan 2 rotates, and the rotation of the capstan 2 is transmitted to the actuator arm 3 via a steel belt, which in turn rotates. do. When the actuator arm 3 rotates, the shaft 4 also rotates, the head arm 5 fixed to the shaft 4 also rotates, and the position of the head 7 changes.

The head positioning accuracy of this type of magnetic disk device is required to within several μm, and in the conventional example shown in FIG. 1, the length of each component changes due to thermal expansion.
There was a drawback that the head position changed due to temperature changes. In other words, when writing to a magnetic medium at a low temperature and reading a signal from the magnetic medium at a high temperature, the length of each component changes, so the position of the head differs between writing and reading, and the signal S/
This resulted in poor N and errors. This phenomenon occurs particularly as the recording density in the radial direction of the magnetic medium increases.

OBJECTS OF THE INVENTION The present invention aims to eliminate the above-mentioned drawbacks of the prior art, and aims to minimize the displacement of the head due to thermal expansion.

Structure of the Invention In order to achieve the above object, the present invention provides an expansion mechanism having an electrostrictive element or a magnetostrictive element in at least one of the head support member and the rotational force transmission mechanism, and transmits an electric signal to the electrostrictive element or the magnetostrictive element. By applying this, the head position is corrected.

DESCRIPTION OF THE EMBODIMENT FIG. 2 shows an embodiment of the invention. In FIG. 2, the same parts as in FIG. 1 are given the same numbers. Reference numerals 8 and 9 indicate notches formed in the middle of the actuator arm 3 and head arm 5, respectively, and an expansion and contraction mechanism having an electrostrictive element or a magnetostrictive element is provided in these notches 8 and 9.

FIG. 3 shows an embodiment in which electrostrictive elements 10, 10' are provided in the notch 8 of the actuator arm 3. In FIG. 3, reference numeral 11 is a U-shaped elastic body whose both ends are inserted into the notches 8, and electrostrictive elements 10, 10' are held between the U-shaped elastic bodies 11. 12 is an electrode provided between the electrostrictive elements 10 and 10'. When an electric field is applied to the electrostrictive elements 10 and 10', strain occurs, and this strain is magnified and transmitted to the actuator arm 3. 13 and 13' are lead wires.

FIG. 4 shows another embodiment of the invention. In FIG. 4, 14 is a magnetostrictive element whose end is fixed to the edge of the opening of the notch 8, 15 is a coil wound around the magnetostrictive element 14, and 16, 16' are lead wires. When a current flows through the coil 15 through the coil 16', a magnetic field is applied to the magnetostrictive element 14, causing distortion, which is transmitted to the actuator arm 3.

In addition, in FIGS. 3 and 4, the electrostrictive element 1 is
0,10', a telescopic mechanism consisting of a magnetostrictive element 14,
A similar extension mechanism is provided in the notch 8 of the actuator arm 3, but a similar extension mechanism is provided in the notch 9 of the head arm 5.
It may also be provided in the actuator arm 3.
Alternatively, it may be provided only on one side of the head arm 5.

FIG. 5 shows the operation of an embodiment in which the head arm 5 is provided with a telescoping mechanism. In the state shown by the solid line in FIG. 5, the electrostrictive element 10 configuring the expansion and contraction mechanism,
When a current is passed through the magnetostrictive element 10' or the magnetostrictive element 14 through the lead wire, distortion occurs, one side of the head arm 5 stretches, the head arm 5 bends as shown by the dashed line, and the head position changes. It should be noted that the electrostrictive elements 10, 10' and the magnetostrictive element 14 expand and contract in only one direction due to voltage or magnetic field, and the expansion and contraction mechanism in the above embodiments expands and contracts only in the stretching direction or only in the contracting direction. be.

Next, a method for controlling correction of track deviation in an embodiment using the above-mentioned expansion and contraction mechanism will be explained.

Figure 6 shows the relationship between the positional deviation between the write head position and the read head position and the head output.If the head positional deviation is large, the head output decreases, and if the positional deviation occurs by approximately the track width, the head output will decrease. The head output becomes almost zero. Normally, when a signal is written to a magnetic medium at one temperature and read out at a different temperature, the thermal expansion of the head drive mechanism causes the track to shift and the head output to decrease. If the track deviation is very large, the head output will be very low and errors will occur. In particular, when the track density is increased, the head output is significantly reduced even if a slight track deviation occurs.

As shown in Figure 7, if the head position deviates by δ at high and low temperatures, when writing or reading signals while applying a displacement larger than δ in advance with the expansion mechanism, the average of the signal output or its envelope By applying voltage to the telescoping mechanism so that the value is maximized, the head's track deviation can be corrected. FIG. 7 shows that a signal is written with a shift of a (a>δ) at a low temperature.
At high temperatures, writing is performed with a shift of b (b>a−δ),
When reading, FIG. 7 shows that it is sufficient to keep the output at the maximum while approaching the head from bottom to top.

Conventionally, the track density was increased by using a linear actuator and controlling the track by a servo track, but according to this embodiment, the track density is increased by using a stepping motor and a simple telescoping mechanism. This allows for higher density.

Effects of the Invention The present invention has the above-described configuration, and has the advantage that track deviation can be corrected with a simple configuration and that track density can be increased.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a conventional head positioning device.
2 is a perspective view of a track position correction device according to an embodiment of the present invention, FIG. 3 is a top view of the main parts of the same device, and FIG. 4 is a top view of the main parts of another embodiment of the invention. FIG. 5 is a top view of another embodiment, FIG. 6 is a diagram showing the relationship between head positional deviation and head output, and FIG. 7 is a diagram showing the head position at low and high temperatures. 1... Stepping motor, 2... Capstan, 3... Actuator arm, 4... Axis, 5
... Head arm, 6 ... Head spring, 7 ... Head, 8, 9 ... Notch, 10, 10' ... Electrostrictive element, 11 ... Elastic body, 12 ... Electrode, 13, 1
3'... Lead wire, 14... Magnetostrictive element, 15...
Coil, 16, 16'...Lead wire.

Claims (1)

[Claims] 1. A rotational drive mechanism, a rotational force transmission mechanism that transmits the rotational force generated by the rotational drive mechanism to the head support member to change the head position, and a rotational force transmission mechanism formed on either the rotational force transmission mechanism or the head support member. A notch, a telescoping mechanism having both ends fixed to the notch, and an electrostrictive element or magnetostrictive element that generates distortion according to a control signal, and a telescopic mechanism that detects the head output and detects track deviation based on the magnitude of the signal. A track position correcting device comprising a discriminating means for discriminating, and a correcting means for correcting the head position using the control signal when the track deviation becomes large based on the output signal of the discriminating means.